A transmission may upshift from a lower gear to a higher gear to allow a prime mover (e.g., an engine or an electric machine) to operate at an efficient operating speed while a vehicle in which the prime mover and the transmission reside continues to accelerate. During an upshift, the prime mover may be decelerated to reduce a torque increase that may occur at the end of the upshift at the transmission output shaft. However, it may be difficult to get the prime mover to decelerate at a desired rate and reduce a torque disturbance at the transmission output shaft since the prime mover is accelerating just before the shift begins. Consequently, the transmission output torque may increase more than is desired as a result of an upshift.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for shifting a transmission, comprising: coupling an engine to a transmission in response to a request to upshift the transmission.
By coupling an engine to a transmission in response to a request to upshift the transmission, torque at the transmission input shaft may be reduced so as to reduce transmission output shaft torque after the shift. In particular, a driveline disconnect clutch may close in response to a transmission shift, thereby reducing torque at the transmission input shaft. A portion of torque applied to the transmission input shaft can be used to rotate the engine so that the transmission output shaft torque may be reduced. Additionally, after the shift is complete or during the torque phase of the shift, engine torque may be provide to the driveline so that vehicle acceleration may be maintained.
The present description may provide several advantages. In particular, the approach may reduce driveline torque disturbances during upshifting. Additionally, the approach may allow engine torque to be available to the driveline after the shift.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.